Validation of ICD‐10 Diagnosis Codes for Identification of Acute Myocardial Infarction From a US Integrated Healthcare System

PURPOSE: Contemporary epidemiologic research on acute myocardial infarction (AMI) using electronic health records (EHR) relies on International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) codes, but limited studies have been conducted to validate these codes in the United States. Therefore, this study aimed to validate AMI events identified by ICD-10-CM diagnosis codes. METHODS: The study was conducted as part of a hepatitis B vaccine safety study. Suspected cases of AMI were identified using ICD-10-CM codes (I21.* or I22.*) in any diagnosis position from August 7, 2018 to November 30, 2020. Cases were adjudicated independently by two cardiologists, with a third resolving disagreements. Positive predictive value (PPV) was calculated as the percentage of suspected cases that were confirmed as definite or probable AMI on review, and exact binomial 95% confidence intervals (CI) were estimated. RESULTS: Of 202 potential AMI events identified among 69 625 individuals, 162 (80.2% 95% CI: 74.0%-85.5%) were confirmed. Encounters with AMI coded as the principal discharge diagnosis code were more likely to be confirmed (86.8% 80.5%-91.6%) than those with AMI in another diagnosis position (55.8% 39.9%-70.9%), while patients with a history of congestive heart failure and peripheral vascular disease had lower PPV compared to those without (83.2% 76.7%-88.6% and 82.9% 76.4%-88.3%, respectively). CONCLUSION: We found that over 80% of AMI cases identified with ICD-10-CM codes were confirmed upon cardiologist adjudication. Cases not coded in the principal diagnosis position were much less likely to be confirmed, and care should be taken when using them in EHR-based research.